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Economic and dam related articles

Dworshak Leak Leads to Repairs

by Staff
KLEW News, July 25, 2008

AHSAHKA - U.S. Army Corps of Engineers workers quickly stopped the flow of water when a malfunctioning regulating outlet gate at Dworshak Dam began to leak water into a machinery room Thursday night at about 10:30 p.m.

On Friday, Walla Walla District operations officials issued a news release about the incident.

Officials explained that Dworshak Dam has three regulating outlet gates controlling the flow of spill water from the reservoir to the Clearwater River. The spill supports fish passage in the lower Snake River by supplementing flows and helping control water temperature.

Officials at the dam said Outlet Gate-2 was passing water and did not fully close during operations, yesterday afternoon. The outlet gate could not be safely inspected to determine the problem because the bulkhead, a water-stop device lowered by crane into position to stop water from entering the gate areas of the dam, was already in use at Outlet Gate-1 by workers performing planned maintenance.

In response to the Outlet Gate-2 malfunction, workers accelerated their maintenance tasks on Outlet Gate-1 and prepared to move the bulkhead from Gate-1 to Gate-2.

At about 10:30 p.m. the Gate-2 leak increased, causing water to flow into the machinery room, down a maintenance passageway and out the downstream face of the dam. Maintenance crews worked late into the night to finish repositioning the bulkhead and stopped the water flow at about 3:30 a.m. Friday. After the leak stopped, crews inspected Outlet Gate-2 and noticed the pin connecting the cylinder to the top of the gate worked itself free, preventing workers from raising or lowering the gate.

"We are conducting an assessment to ensure we know what transpired and determine what repairs are needed," said Walla Walla District's Chief of Operations Division Scott Ross. "There was never a threat to the dam or public safety. The mechanical damage to the gate is repairable. The force of the water caused some secondary damage to lighting and related equipment in the maintenance passageway and machinery room, which we will repair as well."

Ross said the response was quick and according to the book.

"Dworshak's crew did exactly what was needed for this situation - they worked all night and got it fixed," he said. "This is typical for this professional group. They came together in a time of need and used excellent teamwork to resolve the issue. The dam is safe and stable."

In February the Corps of Engineers released a report that included information about concerns over seepage and leakage through the dam's foundation and joint drains. This causes what is called uplift pressure, and could lead to cracks in the dam's monoliths. At the time of the report, dam officials said there were no cracks in the dam itself.

The report resulted from a review that is being conducted on all of the dams across the country.

Dworshak Leak Leads to Repairs
KLEW News, July 25, 2008

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